<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .bg-red {
        background-color: red;
      }
    </style>
  </head>
  <body>
    <div id="app">
      <ul>
        <li
          v-for="(item, index) in list"
          :class="{ 'bg-red': index === active }"
          v-on:click="active = index"
        >
          {{ item }}
        </li>
      </ul>
    </div>

    <script src="./Vue3.js"></script>
    <script>
      const { createApp } = Vue;

      createApp({
        data() {
          return {
            list: ["1111111111", "2222222222", "333333333"],
            // show: true,
            active: 1,
          };
        },
      }).mount("#app");
    </script>
  </body>
</html>
